The invention relates to a hydraulic unit.
Such a hydraulic unit is known from DD 46 600.
The known hydraulic unit has the disadvantage that a delayed movement of a piston in a section of the hydraulic cylinder located between the first and second end position is not possible for a precisely specified position.
Such hydraulic units are widely known in accordance with the state of technology. For example, they are used to generate an opening and closing movement of a gripper installed on a transfer. To attenuate the opening and closing movement of the gripper at the end of the particular path of motion, one usually uses hydraulic cylinders with a so-called end position attenuation. With this, the hydraulic cylinder and a piston installed therein work together on the ends of the hydraulic cylinder with a suitable geometrical embodiment so that the hydraulic oil is forced through a narrowed cross section when the end position is reached and the movement of the hydraulic cylinder is thus delayed or attenuated in the vicinity of the end position.
In particular, hydraulically operated grippers are usually constructed so that the end positions of the hydraulic cylinder correspond to a maximum opening or closing position of the gripper arms of the gripper. In the maximum closing position, the gripper arms are usually resting flat on each other. However, when a work piece is gripped with the gripper arms, this gripping position usually corresponds to a middle position of the piston contained in the hydraulic cylinder. The movement from the maximum opening position to the gripping position takes place without any attenuation whatsoever.
Due to this, undesired pressure shocks in hydraulic unit occur when the work piece is gripped.
Object of the invention is to eliminate the disadvantages in accordance with the state of technology. In particular, a hydraulic unit is to be specified which is as simple and inexpensive to manufacture as possible and which permits an attenuated movement of the piston in a middle section of the hydraulic cylinder located between the first and the second end position. In particular, the movement should be able to be delayed with a precisely specified position in a section located between the first and second end position. In accordance with a further goal of the invention, the hydraulic unit is be able to be operated to the extent possible with conventional hydraulic cylinders.